This invention is directed toward a porous random fiber composite sheet and process for preparing a porous random fiber composite sheet. The process employs a water-soluble cellulose ether in the preparation of the composite sheet which is subsequently dissolved out of the sheet with cold water. The sheet so formed has voids wherever the cellulose ether was present.
The preparation of a random fiber composite sheet is described in U.S. Pat. No. 4,426,470 to Wessling et al. The random fiber composite sheet, also referred to as a reinforced polymer composite or polymeric composites, generally employs wet-laid aqueous techniques such as disclosed in U.S. Pat. Nos. 4,426,470 and 4,431,696. Additionally, foreign patents disclose the wet-laid aqueous procedures to produce polymeric composites. Such patents include U.K. patent No. 1,263,812; French Patent Publication No. 2,507,123 and European Patent Office Publication No. 0,039,292-Al.
While the foregoing procedures can be employed to form solid continuous sheets of reinforced polymer, it would be desirable to be able to form a sheet which is permeable or porous. Such sheets could be advantageously employed as filter media, baffles, battery separators or in other applications where a high strength reinforced porous sheet is desired. Additionally, by adjusting the polymeric content of the sheet various physical properties could be achieved from a stiff porous sheet to a flexible porous sheet.